Actually this is how Brinell testing is done. It is one of the more accurate ways of testing hardness and is done by using a ball fired on an surface with a set force. (A sharp blow). Then the size of the indent is compared using an optical comparitor to a set of know hardness indents and the size of indent that the test indent makes corresponds to the objects hardness. This is a very scientific test of hardness with very repeatable results.
As to how hard to ignite a primer maybe not due to possible variances in primer compounds and maybe anvil construction. Though, I doubt primer compounds or anvils vary that much. But, as far as how hard it is to dent and then flatten a brand of primer when it is recoiled into the face of the recoil shield, bolt face or what have you, it would be very accurate.
Have you read the PDF?
Yes, the firing of a ball with a sharp blow is the correct test.
The cited "study" did not do that. They did this:
"A hardness test rig shall apply 50lbf to a conical anvil for a duration of 30 seconds."
Nooptical comparitor was used and the same primer that was dented was also fired
The test was done by Fort Wayne Tactical LLC